1. Field of the Invention
This invention relates to a composition useful as an all-weather surface material for racetracks, especially horse racetracks.
2. Background
Currently, most horse racetracks are covered with a clay surface and are commonly referred to as "dirt" tracks. Recent studies at the Massachusetts Institute of Technology has reported an article in The Blood-Horse of Mar. 25, 1989, pp. 1704-08 entitled "The Race for Safety," have shown that the risk of injury to a racehorse is directly related to the degree of compaction of the surface upon which it is being raced and the amount of force brought to bear upon the horse's front legs. Dr. Pratt, who carried out this research, explained that during use ordinary dirt tracks undergo a great deal of compaction under the action of horses' hooves. This compaction is greatest on the track area immediately beneath the horse's hooves. Consequently, the track develops areas of high compaction and areas of lesser compaction. When running at speed, therefore, the bones of the horse's legs could experience very different load factors depending upon the area of the track upon which the hoof impacts. The study indicates that uneven loading of a horse's leg bones is a key factor in fatigue with consequent fracture when the maximum level of fatigue endurance is exceeded.
In order to improve "dirt" track conditions, Dr. Pratt indicates that the moisture content of the track should be kept within a window of about 7-11% water. The ordinary water truck used at racetracks to moisten the track increases track moisture by about 0.3 of one percent per pass. Thus, on a hot, dry day, the loss of water due to evaporation may not be replenished adequately by use of a water truck.
Racetrack surface materials using synthetic binders offer the potential for producing a surface more resilient than a "dirt" track. However, thus far efforts in this direction have not produced altogether successful results. For example, the commercially available product, EQUITRACK, sold by En tout cas has significant disadvantages. Racetracks typically include a base layer or "pad" which is a compacted base 2-4 inches thick covered by a "cushion" of looser, granular material which is about 2 inches thick. At the track installation stage, the base or "pad" based on the EQUITRACK material is not easily formed when ambient temperatures rise to typically encountered Summer daytime temperatures, ambient temperatures above about 80.degree. F. Under these conditions, the EQUITRACK material loosens and softens and cannot be easily formed into the desired compacted pad. Further, the track material requires a settling-in period of several months during which the pad has to be regularly worked until it is established. Finally, the EQUITRACK composition, which tends to become sticky in direct sunlight, forms clumps when it cools creating "false pads." These clumps prevent effective raking to form a proper cushion and also fouls maintenance equipment.
There yet exists a need for a racetrack surface composition that provides ease of installation, does not require long periods of time to establish a pad, provides a suitable, resilient cushion and that is readily rakeable and easily maintained.